Pure Javascript implemented Salsa20 cipher.
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README.md

A Salsa20 implementation in pure JavaScript for NodeJS

Designed by Daniel J. Bernstein, The Salsa20 is a stream cipher constructed with a hashing function. This file provides a pure JavaScript implemented Salsa20 encrypt/decryptor.

This library currently provides a seek function for setting counter values. But whether the seek function is compatible when cutting into the middle of the stream, is unknown(I've not tested this).

If you decide to use this library, remember that this cipher takes your first 8 bytes of the key as IV and the reset 32(128bit) or 64(256bit) bytes as the real encryption key. Stream with such same IV and keys can NOT be safely used repeatedly!

This is the version 0.1.2 of this library with a few changes.I've dropped the use of the buffer in NodeJS. All inputs and outputs are ArrayBuffers. If you have encountered any incompatible issues, please have a look at example.js again.

WARNING: This module is written by someone who have no rich experiences in programming with JavaScript. The algorithm is partially verified against the specification, but other security vulnerabilities will possibly exists. The code is NOT reviewed by any cryptographer! Use this at your own risk, you have been warned!

And also note, that this module is licensed under GPLv3.

Known Issues

  1. Sorry for that, but this version may be not backwards compatible (version 0.0.1), some serious errors occurred in the previous version. This may be a big bad news for you if you've encrypted something with this library :(

Usage

The salsa20 is initialized with parameter of rounds(in the specification, this is 10. You can make it larger, e.g. 14, or 20, this may enhance the security, but will slow the speed).

All other inputs, namely, the key, the plaintext or the ciphertext are ArrayBuffers. The processes are always blocking.

The first 8 bytes of the key is taken as nonce, the rest following 16 or 32 bytes are taken as real encryption key. Depending on whether it's 16 or 32 bytes, according to the specification, there will be slightly internal differences in processing. But you can ignore this.

var salsa20 = require('/PATH/TO/THIS/MODULE.js');

// encrypt:
var encryptor = new salsa20(12).key(KEY); // 12 is the round number
var CIPHERTEXT = encryptor.encrypt(PLAINTEXT);

// decrypt:
var decryptor = new salsa20(12).key(KEY); // 12 is the round number
var DECRYPTED = decryptor.decrypt(CIPHERTEXT);

You may also want to view the example.js for examples, and test.salsa20.js for a test under NodeJS against several test vectors.

References

[1] Another implementation in Javascript at: https://gist.github.com/dchest/4582374

[2] Daniel. J. Bernstein, Salsa20 specification, retrived 2014/05/18 from: http://cr.yp.to/snuffle/spec.pdf